1. Field of the Invention
The present invention relates to a method and device for detecting foreign matters and defects produced in the manufacturing processes of LSIs, liquid crystal substrates, etc. wherein patterns are formed on the substrates.
2. Description of the Related Art
In the past, as disclosed in Japanese Patent Laid-open No. 62-89336, such a method for detecting foreign matters and defects on a semiconductor wafer is known that a laser beam is irradiated on the semiconductor wafer and scattered light from foreign matters is detected when there are such foreign matters on the semiconductor wafer and the foreign matters and defects are inspected by comparing the scattered light with an inspection result of a semiconductor wafer of the same kind inspected in advance.
In the conventional device for inspecting foreign matters and defects, a CCD sensor has been used as a photo-detector. A CCD sensor is capable of imaging more than 1,000 pixels at the same time and reading them at high speed. Therefore, by using it as a detector of the device for inspecting foreign matters and defects, it is possible to shorten the inspection time. However, the CCD sensor has a problem of causing electric noises when converting a signal charge generated inside by photoelectric conversion into voltage and reading it. Therefore, when detecting smaller foreign matters and defects, the weak detected signal gained by detecting reflected and scattered light from those smaller foreign matters and defects may buried in electric noises and the smaller foreign matters and defects cannot be detected.